Originally Posted by thrsanne
Hey guys! Sorry if this question has already been asked, but does the shape of the tank matter? I have a 16g tank in my basement that isn't occupied, and was wondering if I can use it to start up a sorority. It's like one of those semi-circle tanks. Haha, thank you, it's a silly question, but I just want to be sure. XD
Its actually a good, if deep, question.
Primarily Betta don't like really high water levels. They're happy in six inches, I had one Roundtail that liked three inch water so much he'd sit on top of a potted plant instead of anywhere else in the tank.
The problem with shallow water is it doesn't give *US* a pretty looking tank. Koi are happy in just about twice their body height which for a fish their size is rather odd, in this circumstance we like to keep them where we can see them. That said a tank that is thin from front to back keeps the fish out where we can see it, such as the "Betta Wave" tank from Aqua-tech, a 2.5g tank nearly as wide and tall as a full five gallon tank. 55g tanks are also tall and wide but have no off-wall depth. They're display tanks.
Generally I've found that the girls themselves are happy in just about any water volume as long as they have friendship and things to do. I've never had one feel dwarfed like the males can in 20g and 29g tanks when alone. (One male actually only played around in about 4g of a 10g.) So the question boils down to what is actually good for the sorority itself; passing lanes!
I'd say to limit the number of girls based on the bottom dimensions of the tank. Lemme find a link here... http://alysta.com/books/fishtank.htm
See where the 10g and 15g have the same bottom dimensions? The most girls I've ever had happy in a 10g is fourteen, believe it or not (and do NOT do it at home). If you're not awesomely experienced with heavy filtration equipment, plants, substrate, water quality control and fish health care don't ever violate the inch-gallon rule. When I had fourteen in the tank I had enough filtration for a 90 gallon tank running with highly optimized water flow and simply the stress on the water was too high, over-stocking "always" leads to crisis, many are controllable but all are of the deadly nature. Digress do I? So for a 15g tank of the 20x10 base dimensions I'd limit it to the same 8 or so girls that you'd have in a normal 10g tank. Make sure to cultivate some plants for the girl's emotional health if nothing else.
With proper filtration, lighting, plants and water control you can probably have twelve girls in the sixteen without ever having an issue involving tank load. Do everything but the fish first.
The other concern is the girls themselves. Some girls like to be alone, some girls like the buddy system and some girls run around saying HI! to everybody all day. For this reason the advice I give is "get five then get a new girl every other week but only if all the girls have a quiet place where they DO sit still. Betta sleep, they sleep deeply sometimes, and a lack of sleep can lead to irritability and aggression. Soft loose plants like Red Wendtii and Bronze Wendtii are great, I've had five or six girls nuzzle into the same plant and nap there. Plants like Anubias are bad because they're JUST plants (and Anubias especially because the girls can uproot it) and have no real use to the girls themselves.
Don't exceed inch per gallon.
Don't have so many girls that they MUST get close to each other in order to get air.
Don't have so many girls that they can't all sleep at the same time.
Do have soft places to rest and hide that won't get uprooted or stuck.
Do have entertainment inside and outside the tank.
Do have plants. Betta love plants. Plants mean food to them, they're bug eaters and its wired deep in their heads. I raised Fluffy (male crown) without a plant then introduced him to one and he loved on it, spent time with it, cared for it, pushed them to safety when they were uprooted and he pined away at one that died. Really, sat and looked at it with fins drooped.
I'm gonna toss a target number at you of nine girls and suggest an Aquaclear 30 with airstone in bottom sponge or an Aquaclear 20 + 5g Hydro-Sponge. Aquaclear filters can be throttled up and down at will and need. Aeration itself kills more than half the aquatic bacteria that kill fish.